A reduction gear (conventional art 1; see FIG. 4) in which multistage reduction mechanisms are combined using parallel-axis-gears (helical gears, for example), or a reduction gear (conventional art 2; see FIG. 5) in which a single stage reduction mechanism and a couple of planetary gear set are combined using parallel-axis-gears is known as a conventional reduction gear for an electric vehicle (see Non-Patent Document 1). The reduction gear according to the conventional art 1 has a merit of a simple structure and less number of components. The reduction gear according to the conventional art 2 has a merit of a compact size of a transmission because deceleration can be done in a condition that a rotation shaft of a sun gear portion 203b and an output shaft 207 are coaxial in the planetary gear mechanism.
[Non-Patent Document 1]
    Nagata, Hisao, et. al., “Toyota three wheel type battery-powered forklift “GENEO-E””, Toyota Jidoshokki Giho, Kabushikikaisha Toyota Jidoshokki (TOYOTA INDUSTRIES CORPORATION), No. 47, p 33-39 (2003, July).